OTHER CONDITIONS AND PROBLEMS 161 



laterals, and all tile should range larger than for similarly 

 placed tile in ordinary systems in humid regions. 



Tile should not be laid, generally, less than 4.5 feet deep. 



The fall in any case should not be less than 0.1 foot 

 for 8-inch tile and 0.2 foot for 4-inch tile. 



Long lines of tile should be avoided. Silt basins should 

 be installed at frequent intervals. 



Flooding is frequently necessary to remove accumula- 

 tions of salts, and where hard pans exist, blasting is fre- 

 quently necessary to facilitate the leeching. 



The drainage waters of most of these systems must be 

 lifted by pumps. 



Tile drains under orchards, vineyards, and other 

 perennial vegetation are subject to clogging from roots. 

 When installing such a system, provision should be made 

 for the future cleaning of the drains. Silt basins should 

 be placed at reasonable intervals, and in each line be- 

 tween basins there should be placed, when laying the 

 tile, a small steel cable. When evidences of root clogging 

 appear, a steel brush of proper size is hitched to (usually) 

 the lower end of the cable and drawn through the line of 

 tile. A second cable is first attached to the brush to be 

 drawn through after it to replace the cable thus pulled 

 out. A frame carrying a pulley set opposite the opening 

 of the tile drains should be placed in silt basins to carry 

 the cable and prevent its injuring the tile. 



Tile drains are likely to clog if water-table is permitted 

 to remain too high. 



211. Cost of tiling. The cost of tile and of hauling and 

 distributing it are matters that can be fairly easily de- 

 termined for any particular job. The cost of tile laid down 

 at the nearest station will depend upon its distance from 

 the factory. The cost of hauling will depend on the dis- 



